1. Field of the Invention
The present invention relates to a material for forming a protective film or the like used in, for example, electronic parts, particularly, a radiation-sensitive resin composition suitable for use as a material for forming an interlayer insulation film in a liquid crystal display device or the like, a process for forming a patterned insulation film using this radiation-sensitive resin composition, an active matrix board having an interlayer insulation film composed of this radiation-sensitive resin composition, a flat-panel display device equipped with this active matrix board, and a process for producing the flat-panel display device.
2. Description of the Background Art
At present, a flat-panel or plane type display device, for example, a liquid crystal display device or the like comes to be utilized as a display screen for OA apparatus, for example, personal computers or the like, or household electric apparatus, for example, televisions or the like. As such a liquid crystal display device, an active matrix type liquid crystal display device using a thin film transistor (hereinafter referred to as “TFT”) as a switching element is widely used.
The active matrix type liquid crystal display device is equipped with a TFT array board obtained by forming, on the surface of a transparent glass substrate, a TFT active matrix circuit in which plural scanning lines and plural signal lines are formed in the form of a matrix, and switching elements each composed of TFT are arranged in the vicinity of positions at which the scanning line and the signal line intersect. This TFT array board can be produced by repeatedly conducting a patterning step of forming a minute pattern by, for example, a photolithographic process.
More specifically, this process is conducted by repeating, as needed, a series of steps including, for example, a film-forming step of forming an insulation film, a semiconductor layer, a metal layer and/or the like on a substrate, a resist-applying step of applying a photosensitive resist for forming a pattern, an exposing step of conducting exposure wherein a proper mask having a prescribed pattern is superimposed on a photosensitive resist layer formed, a developing step of developing the photosensitive resist in the exposed region to remove it, an etching step of removing a film exposed on the surface by removing the resist in the developing step and a separating step of removing the remaining resist.
In the active matrix type liquid crystal display device, there is known that having a structure that an interlayer insulation film for mutually insulating wirings provided in the form of a layer is formed on the surface of the glass substrate, and a transparent conductor film making up a pixel electrode on the surface of the interlayer insulation film is formed in a state connected to a switching element. According to such a structure, improvement in display quality and high numerical aperture can be achieved. For example, Japanese Patent Application Laid-Open No. 152625/1997 discloses a technique to achieve a high numerical aperture by overlapping a gate electrode and a source wiring with a pixel electrode through an interlayer insulation film.
In order to form the transparent conductor film making up the pixel electrode in the production of such a TFT array board, it is necessary to form a transparent conductor layer on the whole surface of the interlayer insulation film formed on the substrate and subject the transparent conductor layer to patterning treatment, thereby forming a transparent conductor film having a desired shape.
An example of the conventional processes for producing a TFT active matrix board will hereinafter be described.
The TFT array board is produced by using an array board material in which a TFT element 21 making up a switching element is arranged on an insulating substrate 20A as shown in, for example, FIG. 9. In FIG. 9, reference numeral 22 indicates a gate electrode connected to a gate wiring, 23 a gate insulation film for insulating the gate electrode 22 from other components, 24 a semiconductor layer formed on the gate insulation film 23 so as to be placed over the gate electrode 22, 25A and 25B a source electrode and drain electrode, respectively, 26A and 26B an ohmic contact layer composed of n+ Si for connecting the semiconductor layer 24 to the source electrode 25A and an ohmic contact layer composed of n+ Si for connecting the semiconductor layer 24 to the drain electrode 25B, respectively, and 27 a protective layer for protecting the whole TFT element.
As illustrated in FIG. 10, an organic resin material having photosensitivity is applied to an upper surface of the array board material to form a coating, the coating is exposed through a mask having a prescribed pattern for forming a contact hole through which a transparent conductor film making up a pixel electrode, which will be described subsequently, is connected to the drain electrode 25B, and the photosensitive resin in the exposed region is then removed by a developing treatment, thereby forming an interlayer insulation film 30 having the contact hole 32.
After the transparent conductor film 35 formed of, for example, ITO is formed by, for example, sputtering or vapor deposition on the whole surface of the interlayer insulation film 30 including the exposed surface through the contact hole 32 of the drain electrode 25B as illustrated in FIG. 11, a photoresist 51 is applied on to the transparent conductor film 35, the photoresist is exposed through a proper mask, and the photoresist is then subjected to a developing treatment, thereby removing an unnecessary portion of the photoresist (photolithographic treatment) as illustrated in FIG. 12.
After a portion of the transparent conductor film, which is not protected by the photoresist 51, is then removed by using, for example, a chemical liquid or gas (etching treatment) as illustrated in FIG. 13, the remaining photoresist 51 is removed by using, for example, a chemical liquid or gas (separating treatment) as illustrated in FIG. 14, thereby a TFT active matrix board 50 is produced.
In the production process of an active matrix type liquid crystal display device in accordance with such a process as described above, many steps are required for forming the transparent conductor film as a pixel electrode on the interlayer insulation film and hence it involves such problems that, for example, productivity and production yield are low, and great production cost is required.
In order to solve such problems, International Publication No. WO 99/10862 discloses, a technique that thick bank layers (bank) are formed along data lines (sig) and scanning lines (gate), thereby reducing a capacity parasitic on the data lines (sig) and partitioning a region for forming an organic semiconductor film (43) of a thin film light-emitting device (40) to form the organic semiconductor film (43) by an ink-jet method as a process for producing an active matrix type display device, by which, upon production of a display device formed of an organic EL element or color filter, a thick insulation film can be suitably formed about an organic semiconductor film of a thin film light-emitting element without impairing the thin film light-emitting element. Herein, the bank layer (bank) is constructed by a thick lower layer-side insulation film composed of an inorganic material and an upper interlayer insulation film composed of an organic material laminated on the lower layer-side insulation film with a narrow width so that the organic semiconductor film is avoided to come into mutual contact with the upper interlayer insulation film.
For example, International Publication No. WO 99/48339 and Japanese Patent Application Laid-Open No. 2000-353594 disclose, a process for forming an organic semiconductor layer in a region to be coated partitioned by a bank by an ink-jet method, as a process for producing a display device using an EL element or a color filter, in which a variation of film thickness between each of pixels is little, and describe that upon the formation of the organic semiconductor layer, the bank is formed with an organic substance on a bank-forming surface of an inorganic substance, for example, in advance and the surface of the bank is modified by a method of performing a plasma treatment under conditions of excessive fluorine, a method of performing an oxygen gas plasma treatment followed by a fluorine-containing gas plasma treatment, or the like.
For example, Japanese Patent Application Laid-Open No. 2000-223270 discloses a technique that in an electroluminescence element having a light-emitting layer held by 2 patterned electrodes in correspondence to the pattern thereof, at least one patterned layer, the surface wettability of which with a laminate material is increased by irradiation of light, is arranged, and the light-emitting layer is laminated making good use of a difference in wettability between an irradiated site and a non-irradiated site.
However, in the processes of producing an EL element or color filter material by the ink-jet method as disclosed in International Publication Nos. WO 99/10862 and WO 99/48339 and Japanese Patent Application Laid-Open No. 2000-353594, it is necessary to form a bank layer constructed by, for example, a thick lower layer-side insulation film composed of an inorganic material, an upper interlayer insulation film composed of an organic material, laminated on the lower layer-side insulation film with a narrow width in a region to form the organic semiconductor layer, and moreover it is necessary to modify the surface of the bank.
When the interlayer insulation film is formed by a particular patterned layer as disclosed in Japanese Patent Application Laid-Open No. 2000-223270, a photolithographic step, etching step and removing step are required for forming a contact hole for connecting upper and lower electrode materials to each other.
Accordingly, any of the above processes involve a problem that they incur not only increase in material cost, but also increase in apparatus cost by the increased number of steps, increase in area of clean room, or lowering of productivity and production yield, and after all, it is difficult to advantageously produce a flat-panel display device.